Fig. 1.

mib1-dependent Notch activity is required for stripe patterning. a A dorsal view of a wild-type adult fly showing the five regular rows of microchaetae (1–5) on each hemi-notum. The anterior and posterior DC macrochaetae (aDC and pDC) are located at the base of row 5. b Patterning dynamics in the notum⁹: downstream of a bimodal gradient of Dl, a proneural-independent pattern of Notch activity (green) determines the position of the first proneural stripes (proneural activity, red). As the pattern of Notch activity evolves, two additional proneural stripes emerge and SOPs (magenta) are selected within each stripe. c, d GFPm3 (GFP, green) is expressed in two stripes of cells (yellow asterisks) flanking cells expressing high levels of Dl (red; located at the position of the future stripes 1 and 5) in 2.5 h apf wild-type nota (c). The expression of GFPm3 is strongly reduced in mib1 mutant pupae (d). e, f A m3-GFP transcriptional reporter (GFP, green) is expressed at high levels in two stripes of cells (yellow asterisks) flanking stripes 1 and 5 in 2.5 h apf wild-type nota (e). Expression of the m3-GFP transcriptional reporter is strongly reduced in mib1 mutant pupae f Sens, red, marks cells of the DC macrochaetae along stripe 5. g, h Five proneural stripes (GFP-Sc, green) are observed in wild-type 7–8 h apf pupae (g). Note that the expression of GFP-Sc is already resolved to singled-out SOPs in row 5 (Sens, magenta; Dl, red). In mib1 mutant pupae (h), a broad domain of proneural cells expressing GFP-Sc is observed in the region corresponding to stripes 2–4, whereas stripes 1 and 5 can be identified. i Adult mib1 mutant flies exhibit a disordered array of regularly spaced bristles, but no clear pattern of rows, in the DC region of the notum. Bristle density is increased. Scale bar is 10 μm (c: c–h). In this and all other figures, representative images of >6 samples (>2 images per sample), from >2 experiments are shown